@chestnutlabs/gcode-preview-core

The framework-neutral preview controller for the Chestnut Labs G-code Preview stack (design: DD-007). This is the single engine under the Vue, React, Svelte, and Web Component (@chestnutlabs/gcode-preview-element) adapters — parse session + renderer + progress mapper glued into one lifecycle with an immutable-snapshot state model (getState() returns a new identity per mutation; onStateChange notifies), which every framework's reactivity can bridge cheaply.

import { createPreviewController } from '@chestnutlabs/gcode-preview-core';

const preview = createPreviewController();
preview.bindCanvas(canvas);              // resize-observed
await preview.parse(bytes);              // worker parse + progressive build
preview.controls.setLayerRange(0, 42);   // scrub / quality / colors / bed / frame ...
preview.observeProgress(obs);            // DD-006 live progress
preview.onStateChange(cb);               // snapshots: summaries only, never toolpath buffers
preview.dispose();

parse() hands a Uint8Array or ArrayBuffer to the parse worker without copying it, so the buffer you passed is empty afterwards. To parse the same file again (for example a different plate via parse(bytes, { plate: 1 })), keep your own copy and pass bytes.slice() each time. Passing the already-transferred bytes fails with E_POST_FAILED, and the preview keeps working.

Building an adapter for another framework? The portable behavioral suite is exported from @chestnutlabs/gcode-preview-core/testing — runBehavioralSuite(...) is the same parity contract the Vue, React, Svelte, and Web Component adapters pass in CI, and it is the anti-drift firewall for any new integration.

Part of Chestnut Labs G-code Preview · MIT